42 



men of them : Achurum, Ichthydion, Hippopedon, Hippiscus, Leprus, Poepe- 

 dates. Pcdies, Pegasidion, and Macliserocera — they are Mexican. I think, 

 from Charpentier's figure and description of Dactylotum, that it belongs near 

 Pezotettix, and, therefore, have placed it there. The transition from Acridini 

 to Xipliocerini, by Lophacris and Rhomalea, would be gradual, but for the 

 intervention of Monachidiuni; I am not acquainted with this genus, and 

 have given it the present position at a venture. The passage to the Tettigi 

 is abrupt, and. unless the gap is filled by newly-discovered forms, must neces- 

 sarily remain so. 



GEOGEAPHICAL DISTRIBUTION OF THE GENERA AND SPECIES OF NORTH AMER- 

 ICAN ACRIDID^. 



It is somewhat difficult to determine the boundary-lines of the different 

 North American Orthopteral districts, but the most natural appears to be- the 

 division into seven districts, as follows : 



1. British America ; 



2. Eastern United States (from the west line of Missouri, or eastern 



border of the Great Plains, to the Atlantic coast) ; 



3. The Rocky Mountain district ; 



4. The Pacific coast ; • 



5. Mexico ; 



6. West Indies ; 



7. Central America. 



I will, therefore, adopt this division, distinguishing between the northern 

 and southern portions of Nos. 2 and .S l)y the letters n and s in decided cases. 



Distribution of the genera. 



Tryxalis 2s 



Aclinriim 5 



Mesops 2,3 



Opouiala 2,3,5,0,7 



Ichthydiou 5 



Pegasidion 5 



Spbeuarium 5.G 



Pyrgomorpha 2s 



Hippiscus 5 



Machffirocera 5 



Oxycoryphus 3,5 



Chrysochraon 1>2,3 



Acrolopliitus 3 



Pedioscertetes 3s 



Stenobotbrus 1,2,3,5,6,7 



Gomphocerus 2 



Stetheophyma 1,2« 



Tragocephala 2,3,4 



Tomonotiis 3,5 



Tropidolo2)biis 3 



Hippopedon 5 



Stnuroiiotus 3 



CEdipoda 1,2,3,4,5,0,7 



Leprus 5 



Boupedou 3 



Bracbype])lus 3,5 



